The invention relates to a digital correlation receiver, particularly for satellite communications transmission, in which the signal channels or bursts from various ground stations, combined in a time division multiplex (t.d.m.) arrangement and provided with a preamble comprising a synchronizing word, are time staggered at the satellite end, and, relative to the reference burst which marks the beginning of the frame, are combined to form a frame and retransmitted (TDMA).
It is necessary in digital transmission operations to synchronize the receiver to the transmitter, and in point-to-point transmission links this is a relatively simple matter as, in the case of existing synchronism, it is merely necessary to monitor the synchronism, and the redundancy. Consequently, the safeguard may comprise a periodic repetition of the synchronizing word. The problem of synchronization is more difficult in transmissions employing burst operation in which the synchronism must be rederived at the beginning of each burst. The difficulty further increases when the received bursts are not pulse-coherent to one another.
Consequently, steps must be taken to insure that the beginning of the burst, and thus the synchronism of each individual burst, can be ascertained with sufficiently high reliability. While this could be accomplished by a redundant transmission of the synchronizing word or a synchronizing word with fault correction, such a solution has the disadvantage that a greater or lesser number of additional bits is required which thus correspondingly reduces the useful component of the burst, and thus results in a reduction in an economy of the TDMA method.
In the publication "Unique Word Detection in Digital Burst Communications" by W. Schrempp and T. Sekimoto, which appeared in IEEE Transactions on Communication Technology, Vol. 16 Com-16, No. 4, August 1968, synchronizing words of this type are provided for the TDMA transmission method. The synchronizing words are recognized in a receiver by means of a correlation circuit and then a burst-commence-characteristic is derived in such receiver.